Historically, predelinquent children with conduct disorders have been difficult to treat, but recent developments in behavior modification show promise for helping these children. Previous work by the investigators has suggested the feasibility of designing clinical treatment programs for aggressive children based on knowledge of the antecedent environmental events which precipitate noxious behaviors. This proposal seeks to extend these stimulus control investigations by intensive analyses of the environmental determinants of deviancy in preadolescents. The methodology of the previous and proposed work represents a notable first attempt to bridge the gap between operant and assessment paradigms for studying the determinants and structure of deviant behavior in children. The broad goal of the proposal is to provide both theoretical and empirical underpinnings for the design of innovative treatment and prevention programs aimed at manipulating components of the child's environment which produce deviant responses. This goal will be approached via (a) the collection of extensive amounts of data for each of 30 families using a multi-setting, multi-instrument, multi-coder procedure for assessing 29 categories of behavior and environmental descriptors; (b) a series of stimulus control analyses using probabilistic and correlational procedures to identify determinants of aggressive behaviors in the natural environment; and (c) the design, application, and evaluation of experimental treatment procedures based on the stimulus control analyses.